PARIS, May 24 (Xinhua) -- Swiss tennis legend Roger Federer, making his first appearance at Roland Garros since 2015, compared current situation to the 2017 Australian Open with a similar feeling of "unknown".

Asked about his thought of winning the title in the French capital, Federer replied, "Don't know. A bit of a question mark for me. Some ways I feel similar to maybe the Australian Open in 2017."

Federer ended his Grand Slam winning drought for over four years at the 2017 Australian Open at the expense of his old foe Rafael Nadal.

"A bit of the unknown. I feel like I'm playing good tennis, but is it enough against the absolute top guys when it really comes to the crunch? I'm not sure if it's in my racquet," he added.

Already having made his return, Federer can feel the difference between now and then, but it seems that everything has never changed at the same time.

"Center court looks very different. There has been a lot of upgrades and investments made. So you can feel it," he said. "I feel still it is the old Roland Garros. It's kept its flair and everything. When you miss something in life, you're happy to be back there again."

Federer made into the quarterfinals in Madrid and Rome this year, also having saved match points from his opponents en route to victories.

"I have been able to train hard enough and also got the necessary tough matches in Madrid and Rome more than I would have liked to.

"I really feel like playing under pressure, and playing with nerves was important for me so I feel totally ready," he noted.

Federer will start his quest at Roland Garros against Italian Lorenzo Sonego.